Editing Boeing AH-64 Apache (section)

===Advanced Attack Helicopter===
{{main|Advanced Attack Helicopter}}
[[File:Hughes experimental copter.jpg|thumb|right|An early [[Hughes Helicopters|Hughes]] YAH-64 prototype with T-tail]]

After the [[Lockheed AH-56 Cheyenne|AH-56 Cheyenne]] was cancelled in 1972 in favor of projects like the [[U.S. Air Force]] [[Fairchild Republic A-10 Thunderbolt II|A-10 Thunderbolt II]] and the [[United States Marine Corps|Marine Corps]] [[Hawker Siddeley Harrier|AV-8A Harrier]], the United States Army sought an aircraft to fill an anti-armor attack role that would still be under Army command.<ref>{{cite news |title=Army Cancels Helicopter Contract |newspaper= Victoria Advocate |date= 10 August 1972}}</ref><ref>{{cite news |url=https://news.google.co.uk/newspapers?id=j8kPAAAAIBAJ&sjid=No0DAAAAIBAJ&pg=5294,127450&dq=advanced+attack+helicopter&hl=en |title=Army Decides To Scrap Cheyenne Helicopter Gunship |newspaper=Boca Raton News |date=3 September 1972}}</ref> The 1948 [[Key West Agreement]] forbade the Army from owning combat fixed-wing aircraft. The Army wanted an aircraft better than the [[Bell AH-1 Cobra|AH-1 Cobra]] in firepower, performance, and range. It would have the maneuverability for terrain following [[nap-of-the-earth]] (NoE) flying.<ref name=Bishop_p5>Bishop 2005, pp. 5–6.</ref> To this end, the U.S. Army issued a Request For Proposals (RFP) for the Advanced Attack Helicopter (AAH) program on 15 November 1972.<ref name=Army_p10>OAVCSA 1973, p. 10.</ref><ref>{{cite news |url=https://www.nytimes.com/1972/11/16/archives/army-seeking-bids-on-new-helicopter.html |title=Army Seeking Bids on New Helicopter |work=[[The New York Times]] |date=16 November 1972}}</ref> As a sign of the importance of this project, in September 1973 the Army designated its five most important projects as the "Big Five", with the AAH included.<ref>{{cite web |url=https://news.google.co.uk/newspapers?id=H64hAAAAIBAJ&sjid=hpoFAAAAIBAJ&pg=1762,200656&dq=advanced+attack+helicopter&hl=en |title=New Army Tactic |website=Reading Eagle |date=11 September 1973}}</ref>

Proposals were submitted by [[Bell Helicopter|Bell]], [[Boeing Rotorcraft Systems|Boeing Vertol]]/[[Grumman]] team, [[Hughes Aircraft|Hughes]], [[Lockheed Corporation|Lockheed]], and [[Sikorsky Aircraft|Sikorsky]]. In July 1973, the U.S. Department of Defense selected finalists Bell and Hughes Aircraft's Toolco Aircraft Division (later [[Hughes Helicopters]]). This began the phase 1 of the competition.<ref name=Bishop_p7>Bishop 2005, p. 7.</ref> Each company built prototype helicopters and went through a flight test program. Hughes' ''Model 77/YAH-64A'' prototype first flew on 30 September 1975, while Bell's [[Bell YAH-63|Model 409/YAH-63A]] prototype first flew on 1 October 1975. After evaluating the test results, the Army selected Hughes' YAH-64A over Bell's YAH-63A in 1976. Reasons for selecting the YAH-64A included its more damage tolerant four-blade main rotor and the instability of the YAH-63's [[tricycle landing gear]] arrangement.<ref name=Richardson_Peacock_p8>Richardson and Peacock 1992, p. 8.</ref><ref name=Donald_p114>Donald 2004, p. 114.</ref>

The AH-64A then entered phase 2 of the AAH program under which three pre-production AH-64s would be built, additionally, the two YAH-64A flight prototypes and the ground test unit were upgraded to the same standard.<ref name=Richardson_Peacock_p8/> Weapons and sensor systems were integrated and tested during this time, including the laser-guided [[AGM-114 Hellfire]] missile.<ref name=Bishop_p8>Bishop 2005, p. 8.</ref> Development of the Hellfire missile had begun in 1974, originally known by the name of ''Helicopter Launched, Fire and Forget Missile'' ('Hellfire' being a shortened acronym),<ref>{{cite web |url=http://www.boeing.com/history/bna/hellfire.htm |title=AGM-114 Hellfire missile |publisher=Boeing |access-date=30 July 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110914210609/http://www.boeing.com/history/bna/hellfire.htm |archive-date=14 September 2011}}</ref> for the purpose of arming helicopter platforms with an effective anti-tank missile.{{citation needed|date=February 2023}}